This invention relates to protective devices for syringes which protect the user from accidental puncture by the hypodermic needles attached to the syringe. In particular, this invention relates to protective devices for the permanent type of syringe which is repeatedly re-useable for a relatively long period of time before it has to be replaced or discarded.
A protective device for a re-useable syringe should itself be re-useable for the same length of time as the syringe, or re-useable for a significant period of time and readily replaceable if it does have to be replaced before the syringe has to be replaced. For this reason among others, a protective device for the repeatedly re-useable type of syringe requires various construction features not needed by protective devices for the one-time use disposable type of syringe.
Examples of prior art types of protective devices for syringes includes those shown and described in the following United States patents.
U.S. Pat. No. 4,752,290 discloses a needle bearing medical device of the disposable type having a tubular shield which can be held in three positions, one of which is a releasable needle covering position, the second of which is a releasable needle exposing position and the third is a non-releasable needle covering position from which the shield cannot be retracted for re-use.
U.S. Pat. No. 4,738,663 discloses a hypodermic needle shield which comprises a sleeve guide that is mounted on the syringe and secured to its flange, and a shield which travels on the sleeve guide between an extended and retracted position. When in the extended position wherein the shield covers the needle, the shield is locked in place where it can neither be retracted nor pulled off of the syringe but remains in place to cover the needle when the syringe with needle still attached is discarded.
U.S. Pat. No. 4,737,144 discloses a syringe having a protective sleeve that can be pushed forward to cover the needle after it has been used, the sleeve locking in place in the extended position from which it cannot be retracted.
U.S. Pat. No. 4,723,943 discloses a syringe having a sheath with an elongated slot to receive a guide lug on the barrel of the syringe. The rearwardly extending end of the slot in the sheath opens to a recess having a pair of laterally extending pockets or slots, one of which has a snap lock lip and the other has a shape and dimension to receive the lug snugly therein when the sleeve is rotated but from which the lug can be unseated for sliding the sheath back to its retracted position. When the sheath is in the extended position and rotated the opposite way for the lug to seat in the other pocket having the snap lock lip, the sheath cannot be rotated back to get the lug out of that pocket. The sheath is then locked permanently in place and the entire assembly is then discarded.
U.S. Pat. No. 4,702,739 discloses a syringe having a retractable sleeve covering the needle which retracts when the syringe is placed against the body of a patient, or self administrator, and the syringe pushed forward to insert the needle for injection of the medication. It is designed especially for those who have to administer injections to themselves, such as diabetics, and to reduce the fear or anxiety sometimes associated with seeing a needle about to be inserted through a person's skin.
U.S. Pat. No. 4,702,738 discloses a disposable syringe and sheath in which the sheath may be permanently locked in its extended position covering the needle for disposal of the entire unit after being used.
U.S. Pat. No. 4,693,708 discloses a syringe of the disposable type in which the needle is permanently attached and sealed within a tubular enclosure device to protect it from contamination until ready for use, at which time the end tab is torn away to open the forward end wall for the needle to project through when the tubular device is retracted to enable insertion of the needle into a patient. After use, the tubular device is pushed forwardly to cover the used needle and the unit then discarded.
U.S. Pat. No. 4,681,567 discloses a syringe having a slidable sheat to cover the needle and lock permanently in place after the needle has been used.
U.S. Pat. No. 4,631,057 discloses a syringe and sheath in which the forward end of the syringe barrel has a collar with an annular groove to receive a corresponding annular bead of the sheath when in the retracted position, and a one-way annular groove to receive a one-way annular snap lock projection of the sheath to lock it permanently in place when pushed to the extended position.
U.S. Pat. No. 4,425,120 discloses a syringe and sheath in which the barrel of the sheath has a pair of lugs, and the sheath has a pair of L-shaped slots to receive respective ones of the lugs whereby the sheath can be locked in both the retracted and extended positions by rotating to seat the respective lugs in the laterally extending leg of the respective slot.
The protective sheath in accordance with the present invention slides on the barrel of the repeatedly re-useable syringe between a retracted position, in which the screw threads of the needle connecting projection are exposed for connecting a hypodermic needle thereto, and an extended position after the needle has been used to cover the needle until it can be disposed of. Since the syringe in this case is of the re-useable kind, the used needle has to be disconnected from the syringe. The protective sheath therefore is provided with apertures which overlie the hub of the needle assembly when the sheath is in its extended position covering the needle, whereby the user can reach through such apertures to unscrew the hub of the needle assembly from the threads of the needle connecting projection. The needle assembly then drops to the bottom of the extended sheath which the user holds in a horizontal position to prevent the uncoupled needle assembly from dropping out. The unit is then carried to a disposal container whereupon the syringe and its extended sheath can be tipped downward to let the used needle drop through the open forward end wall of the sheath into the container for disposal.
The sheath and syringe barrel include cooperating stop members to prevent removal of the sheath from the forward or needle connecting end of the syringe. The sheat is removable from the syringe barrel for cleaning, sterilization and the like, by unscrewing the syringe barrel from the plunger mechanism and sliding the sheath off from the reward, or plunger connecting end of the barrel. The sheath is replaced on the barrel from the same rearward end, and the barrel then screwed in place in the receiving recess of the plunger assembly.
Some of the permanent re-useable syringes are of the type in which the barrel cavity is bounded by an imperforate wall, and the cartridge of injectable material is placed in the barrel of the syringe from its rearward end while uncoupled from the plunger assembly.
Other types of permanent, re-useable syringes have an elongated slot in the wall of the barrel wide enough and long enough to place a cartridge having the injectable substance in the barrel through such opening or slot in its side wall.
The protective sheath in accordance with the present invention may be used with both types of permanent, re-useable syringes. When used with the type in which the cartridge is placed in the syringe barrel through the opening in its side wall, the sheath is pushed forward to its extended position which exposes the elongated slot or opening to insert the cartridge. The sheath is then moved back to its retracted position which exposes the threads of the needle connecting projection at the forward end of the syringe barrel. When the needle assembly is connected, the syringe is ready for use. After use on a patient, the sheath is moved to its extended position where it completely covers the used needle. The needle assembly is then disconnected as described above while the protective sheath is still in its extended position and the disconnected needle then carried in the sheath held in the horizontal position to the disposal container for disposal of the used needle assembly.
Hypodermic needles come in a two-part sealed cartridge, having a closed cylindrical chamber in which the needle extends with the hub frictionally held by the cylindrical wall bounding the opening and a removable cap which covers the hub until the user is ready to use the needle. When the cap is removed, the internal threads of the hub of the needle assembly are exposed for screwing on to the threaded needle connecting projection at the forward end of the syringe barrel while the needle itself is still within the chamber of the cartridge it comes in. After the needle assembly has been screwed on to the syringe, the cartridge chamber is pulled away to expose the needle. At this time, the sheath of the present invention may be pushed forward to its extended position wherein it completely covers the needle. The syringe with sterile needle attached may then be laid down temporarily without the needle touching a non-sterile surface.
In the prior art practice when it became necessary to temporarily lay the syringe down after a sterile needle had been connected and its original cartridge chamber removed, the users would put the original cartridge chamber back on the needle assembly to protect it from touching a non-sterile surface. This often results in needle sticks while the user tries to insert the needle back into the relatively small diameter chamber of the original needle cartridge. The Center for Disease Control has now recommended that syringe needles not be re-capped after the original cartridge chamber has been removed in order to prevents doctors, dentists and other health care providers from accidentally receiving a needle stick while trying to re-cap the needle.
The protective sheath in accordance with this invention makes it unnecessary to have other devices in the treatment area for the protection of uncapped needles connected to a syringe.
To give the sheath greater stability and to help hold it in axial alignment with the syringe barrel while in the extended position, especially when laid down on a table or the like where forces may be applied against the forward end of the extended sheath tending to move it out of axial alignment whereby its peripheral wall could come in contact with the sterile needle, a plurality of longitudinal ribs are provided on the syringe barrel to seat in a corresponding plurality of longitudinal grooves formed in the wall of the sheath opening to its inner surface. The cross-sectional dimension and configuration of the sheath corresponds closely to that of the syringe barrel for a snug fit but which permits the sheath to readily slide on the barrel between its retracted and extended positions. The longitudinal ribs and grooves enhance and re-inforce the stability of the sheath in axial alignment with the syringe barrel. The sheath has a longitudinal dimension long enough to extend beyond the needle connected to the syringe and with a sufficiently long portion of sheath still on the barrel of the syringe, with the ribs of the syringe barrel seated in the grooves of the sheath, to hold the sheath in axial alignment with the syringe barrel when the sheath is in its extended position
Stop means are provided as set forth in detail in the description of the preferred embodiment to prevent the sheath from moving forward on the syringe barrel beyond its intended point. A releasable lock member is also provided to lock the sheath in its extended position, but releasable to enable moving the sheath back to its retracted position. The lock member is also described in detail later herein.
The sheath is preferably made of a durable long lasting material which is also heat resistant and pressure resistant, such as autoclavable acrylic or a metal such as stainless steel. The sheath is preferably transparent, but it need not be.
While the protective sheath in accordance with this invention is shown and described herein for use with one kind of syringe, it is useable with various other types of syringes which have an elongated barrel, a plunger or other operating mechanism at one end and a hypodermic needle connected at the other end.